Barrier vent assembly

ABSTRACT

The technology disclosed herein relates to a vent assembly having a vent housing that defines a first airflow pathway, a second airflow pathway, and a third airflow pathway. The first airflow pathway is configured for fluid communication with an interior of an enclosure. The second airflow pathway is configured for fluid communication with the external environment, and the third airflow pathway extends between the first airflow pathway and the second airflow pathway. A membrane is coupled to the vent housing such that the second airflow pathway and the third airflow pathway are in communication through the membrane. Coalescing filter media is disposed within the vent housing such that the third airflow pathway and the first airflow pathway are in communication through the coalescing filter media. The vent assembly defines a spacing region between the coalescing media and the membrane.

This is a continuation application of U.S. patent application Ser. No.15/547,363, filed on Jul. 28, 2017, which is a U.S. National Stage Entryof PCT International Patent Application No. PCT/US2016/015387, filed onJan. 28, 2016, which claims priority to U.S. Provisional PatentApplication No. 62/108,932, filed Jan. 28, 2015, the contents of each ofwhich are herein incorporated by reference in their entireties.

TECHNOLOGICAL FIELD

The current technology relates to a vent assembly. More particularly,the current technology relates to a barrier vent assembly.

BACKGROUND

Various types of gearboxes, such as automotive transmissions,differential cases, and power transfer units, generally require somesort of breather vent that allows the pressure between the gearbox andthe external environment to equalize. Some breather vents incorporatefilter media to prevent the ingress of contaminants such as dust andfluids to the gearbox. For example, a microporous membrane can be usedto prevent the entry of water in the gearbox. Oil particles that arepresent in the gearbox, however, can become airborne and lodge into themembrane. Some existing technology uses an oil sorbent (e.g., absorbentand/or adsorbent of oil) filter media that is configured to capture theoil particles before they reach the membrane. However, such vents have arelatively short lifespan because, as the oil particles accumulate inthe media, the media becomes clogged, which decreases the life of thevent. Furthermore, because the sorbent filter media wicks the oilparticles, the oil can foul the membrane relatively quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vent assembly consistent with thetechnology disclosed herein.

FIG. 2 is a cross sectional view of a vent assembly consistent with theembodiment depicted in FIG. 1 in an example implementation.

FIG. 3 is a perspective view of a vent assembly housing consistent withthe technology disclosed herein.

FIG. 4 is a perspective, exploded view of vent assembly componentsconsistent with the technology disclosed herein.

FIG. 5 depicts a cross-sectional perspective view of a vent assemblyconsistent with the technology disclosed herein.

FIG. 6 depicts a perspective cross-sectional view of an alternate ventassembly consistent with the technology disclosed herein.

FIG. 7 depicts a cross-sectional view of another vent assemblyconsistent with the technology disclosed herein.

FIG. 8 is a schematic diagram of an example test set-up.

FIG. 9 is a graph depicting comparative test results of vent assemblies.

FIG. 10 is a graph depicting comparative test results of ventassemblies.

FIG. 11 is a graph depicting example test results of one type ofcoalescing media consistent with the technology disclosed herein.

FIGS. 12a-12b are schematic drawings representing test results for twofilter medias.

FIGS. 13a-13c are schematic drawings representing photographs of dropletcontact angles for example filter media fibers.

FIG. 14 is a flow chart depicting one method consistent with thetechnology disclosed herein.

The present technology may be more completely understood and appreciatedin consideration of the following detailed description of variousembodiments in connection with the accompanying drawings.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of a vent assembly consistent with thetechnology disclosed herein. The vent assembly 100 generally has a venthousing 110 defining a mounting structure 120 and an airflow pathway 150extending from the mounting structure 120 to the environment external tothe vent housing 110 (which will be referred to herein as the “externalenvironment”). The vent housing 110 defines perimeter openings 140 suchthat the airflow pathway 150 extends to the external environment throughthe perimeter openings 140. The vent assembly 100 has a vent cap 130that is coupled to the housing 110.

FIG. 2 depicts a cross-sectional view of the vent assembly 100 in anexample implementation. FIG. 5 depicts a perspective view of the ventassembly 100 and can be viewed in conjunction with FIG. 2 forunderstanding the descriptions herein. From the mounting structure 120,the airflow pathway 150 extends through a coalescing region 180 definedby the vent assembly 100, a spacing region 170 defined by the ventassembly 100, and a membrane 160 coupled to the vent housing 110. Thevent coalescing region 180 is positioned between the membrane 160 andthe mounting structure 130. The mounting structure 120 is mounted to aconnector tube 190 that is configured to engage a connecting portion 202sealably coupled to an enclosure 200. The connecting portion 202 definesa vent orifice 204 leading to the interior of the enclosure 200.

The enclosure 200 is generally configured to contain oil. The enclosure200 can also be configured to contain moving parts, such as gears. Theenclosure 200 can be used for a variety of applications such as, forexample, transmission systems, transfer cases, gear boxes, powertransfer units, axle components, and the like. Such applications canparticularly be found within industries such as automotive,manufacturing, energy production, and the like. Those having skill inthe art will appreciate the wide applicability of the current technologyto a variety of technological fields.

In a variety of embodiments the connector tube 190 is constructed ofrubber, and frictionally engages both the mounting structure 120 of thevent assembly 100 and the connecting portion 202 of the enclosure 200.In the current embodiment the mounting structure 120 defines acircumferential ridge 122 that engages the connector tube 190. Theconnecting portion 202 and the connector tube 190 can engage withsurface friction and/or with physical elements such as barbs and/orother protuberances including ridges and/or bumps. Other approaches canbe used to couple the vent assembly 100 to the enclosure 200, as will beappreciated. The vent assembly 100 can be sealably coupled to theenclosure 200 through other approaches such as with a snap fitting,screw, butt connection, and key and lock, as examples. In manyimplementations an o-ring is used to sealably couple the vent assemblyto the enclosure 200. In some embodiments a mounting structure of a ventassembly can be configured to directly receive an opening defined in anenclosure.

The vent assembly 100 is generally configured to vent the enclosure 200to which it is mounted while preventing the entry of dust, fluids, andother contaminants to the enclosure 200. In one embodiment, the ventassembly 100 is designed to achieve IP69K ingress protection, meaningthat, upon installation, the vent assembly 100 protects the enclosure200 against close-range, high-pressure, high-temperature spray-downs.The vent assembly 100 is also configured to enable the coalescence ofoil droplets and drain the coalesced oil back into the enclosure 200.

The membrane 160 is generally configured to serve as a barrier tooutside fluid and dust contamination for the enclosure 200 whileallowing air exchange between the enclosure 200 and the environmentexternal to the enclosure 200 (such as the atmosphere). As such, themembrane 160 is generally disposed across the airflow pathway 150. In avariety of embodiments, the membrane 160 is coupled to a membranereceiving surface 112 defined by the vent housing 100, where themembrane receiving surface 112 is visible in FIG. 3, which depicts aperspective view of the vent housing 100 without the cap 130 (see FIG.1). In one embodiment, the membrane is pleated to increase airflow.

Various types of materials would be suitable for use as the membrane160. Generally, the membrane 160 is a microporous material, where theterm “microporous” is intended to mean that the material defines poreshaving an average pore diameter between about 0.001 and about 5.0microns. The membrane 160 generally has a solidity of less than about50% and a porosity of greater than about 50%. In a variety ofembodiments, the membrane 160 has a plurality of nodes interconnected byfibrils. In a number of embodiments the membrane 160 is an expandedpolytetrafluoroethylene (PTFE) membrane. The membrane 160 can also beconstructed of polyamide, polyethylene terephthalate, acrylic,polyethersulfone, and/or polyethylene, as other examples. The membrane160 can have the following physical properties: water entry pressure(WEP) of at least 5 psi and a Frazier permeability of greater than 0.275ft/min at 0.5 inches H₂O (0.01807 psi).

In some embodiments the membrane 160 is a laminate. For example, themembrane 160 can be a Tetratex™ grade from Donaldson Company, Inc.,based in Minneapolis, Minn., which is laminated to a non-woven nylonsupport layer such as that available from Cerex Advances Fabrics, Inc.located in Cantonment, Fla. In such an example, the membrane has a WEPof about 9 psi and a Frazier permeability of about 1.8 ft/min at 0.5inches H₂O (0.01807 psi).

In a number of embodiments the membrane 160 is oleophobic. The membrane160 can have an oleophobic treatment. In one particular embodiment themembrane 160 has an oleophobicity rating of 6, 7 or 8 based on AATCCSpecification 118-1992 and ISO 14419.

The coalescing region 180 is generally configured to coalesce and drainoil particles from the air as it passes through the vent assembly 100via the airflow pathway 150 from the enclosure 200. Such a configurationprevents a high percentage of air-bound oil particles from the enclosure200 from depositing on the membrane 160, which can result in poreblockages in the membrane 160, resulting in reduced vent life. Thecoalescing region 180 is configured to enable coalescence of the oilparticles into droplets within the vent assembly 100 and allow the oilto drain out of the coalescing region and back into the enclosure 200.The coalescing region 180 is not a sorbent of oil. In multipleembodiments, the coalescing region 180 is oleophobic in nature, whichcan prevent wicking of the oil against gravity upwards, towards themembrane 160, by reducing capillary action of the coalescing region 180.The coalescing media within the coalescing region 180 can have anoleophobicity of at least about 6.5 based on AATCC Specification118-2013 and ISO 14419. In one embodiment the coalescing region has anoleophobicity of at least about 7, and more particularly has anoleophobicity of about 7.5.

The coalescing region 180 can be a variety of types of materials andcombinations of materials. For example, the coalescing region 180 canhave bi-component fibers. The bi-component fibers can be constructed oftwo different polyesters. In some embodiments, the coalescing region 180can have glass fibers. In at least one embodiment the glass fibers aremicrofibers. Generally, the coalescing region 180 substantially lacks abinder material, where the term “binder material” is defined herein toexclude the fibers in the coalescing region, such as the bi-componentfibers or other fibers. In a variety of embodiments, the coalescingregion 180 of the vent assembly 100 contains coalescing filter media182. Details about the materials used for the coalescing region 180, andparticularly the coalescing filter media 182, will be described in moredetail, below.

Coalescing filter media 182 in the coalescing region 180 of the ventassembly 100 can be a stack of a plurality of layers of synthetic filtermedia. A substantial portion of the layers can be stacked such that eachflow face of each layer of filter media is in direct contact with theflow faces of adjacent layers of filter media. The term “flow face” isused to mean each surface of the filter media that is configured to facethe directions of airflow through the airflow pathway 150. Each of theindividual layers of filter media can have a relatively low particlefiltration efficiency and low pressure drop. Generally, each layer ofsynthetic filter media has a maximum particle filtration efficiency of15%, 10%, or even 8%, wherein “particle filtration efficiency”—when usedherein with regard to a single layer of filter media—refers to theparticle filtration efficiency of the single layer of filter media aschallenged by 0.78 micron monodisperse polystyrene spherical particlesat a face velocity of 20 ft/min, measured according to ASTM #1215-89. Inone particular embodiment, each layer of synthetic filter media has aparticle filtration efficiency of about 7%. In some embodiments eachlayer of synthetic filter media in the coalescing region 180 has aboutequal particle filtration efficiency. The relatively low particlefiltration efficiency of each of the filtration layers can aid in oilremoval by defining a relatively open pathway that provides lessresistance to the coalesced oil when draining out of the coalescingregion and towards the interior of the enclosure 200.

The coalescing region 180 is generally additionally configured toprovide particle filtration. In a variety of embodiments, the coalescingregion 180 has an elongate structure, meaning that the coalescing region180 is longer than it is wide. Such an elongate structure can improveparticle filtration by increasing the overall particle filtrationefficiency of the coalescing region 180 relative to the individuallayers of coalescing filter media 182. The coalescing region 180 canhave an overall particle filtration efficiency of at least 90%, at least95%, and/or at least 99%, wherein “overall particle filtrationefficiency” is used herein to define the particle filtration efficiencyof the coalescing region. The overall particle filtration efficiencyrefers to the percentage of particles that penetrate through thecoalescing region when challenged by oil aerosol at 7.2 liter/min, usingthe test setup depicted in FIG. 8 and described in the correspondingdescription. The particle sizes of the oil aerosol are within the rangeof 0.19-2 micron, with a median particle size of 0.4 micron and a modeof 0.3 micron. The coalescing region 180 can have an initial pressuredrop of less than 1.2 psi, 1.0 psi, or even 0.8 psi, where initialpressure drop is defined as the difference in pressure across thecoalescing region 180 before any substantial amount of particles havebeen captured by the coalescing region 180, when challenged with oilaerosol at a face velocity of 3.94 ft/sec (1.2 m/sec)), using the testsetup depicted in FIG. 8 and described herein.

In a variety of embodiments, the stack of the plurality of layers ofsynthetic filter media 182 can additionally have at least one secondarylayer of coalescing filter media. The at least one secondary layer ofcoalescing filter media can have a particle filtration efficiency thatis different than the rest of the layers of coalescing filter media. Ina variety of embodiments, the at least one secondary layer of coalescingfilter media has a particle filtration efficiency that is greater thanthe particle filtration efficiency of the rest of the layers ofcoalescing filter media. For example, the at least one secondary layerof coalescing filter media can have a particle filtration efficiencythat is at least 15%, 30%, 60%, or even 70%. In one example, the atleast one secondary layer of coalescing filter media can have a particlefiltration efficiency of about 99%.

In embodiments where the at least one secondary layer of coalescingfilter media has a relatively higher particle filtration efficiency, itcan be desirable to position the at least one secondary layer of filtermedia away from the enclosure 200 due to the higher risk of fouling uponcontact with oil from the enclosure 200. In at least one embodiment, theat least one secondary layer of coalescing filter media is positioned inthe stack of layers of filter media towards the microporous membrane. Inone particular embodiment, the at least one secondary layer ofcoalescing filter media is directly adjacent to the spacer region 170.In such an embodiment the at least one secondary layer of coalescingfilter media would be the top layer of the stack of layers of filtermedia 182.

The at least one secondary layer of coalescing filter media can increasethe overall particle filtration efficiency of the coalescing region 180and/or reduce the overall length of the coalescing region 180 to achievethe desired overall particle filtration efficiency and thereby reducethe length of the filter pack. The at least one secondary layer ofcoalescing filter media can be treated for oleophobicity, as discussedabove. In another embodiment, the at least one secondary layer ofcoalescing filter media is not oleophobic. In one embodiment the atleast one secondary layer of coalescing filter media is consistent withmedia layers described in U.S. Pat. No. 7,314,497, issued on Jan. 1,2008, which is incorporated herein by reference.

In a variety of embodiments the stack of the plurality of layers offilter media 182 has the number of layers of filter media that issufficient to achieve the target overall particle filtration efficiencyof the coalescing region 180. In some embodiments, the stack of theplurality of layers of synthetic filter media 182 has at least 2, 25,50, 60, or even 70 layers of filter media. In one embodiment thecoalescing region 180 has about 90 layers of synthetic filter media.Typically the total depth of the layers of filter media will be about0.5 inches (12.7 mm) or more, and in one embodiment about 1.8 inches(45.7 mm) depending on the overall particle filtration efficiencydesired.

Generally, each of the plurality of layers of filter media is stackedwithin the fluid pathway such that some of the layers are non-alignedwith some other of the layers of filter media. In other words, each ofthe layers of synthetic filter media has a central axis, and, whenstacked, a plurality of the central axes would not be collinear. In someembodiments, at least a portion of the layers of synthetic filter mediahas a flow-face area that is larger than the correspondingcross-sectional area of the airflow pathway 150. Such configurations canprevent air from flowing through the airflow pathway 150 without passingthrough at least a portion of the plurality of layers of syntheticfilter media.

In a variety of embodiments, a substantial portion of each layer of thestacked layers of synthetic filter media 182 in the coalescing region180 is substantially unbonded to adjacent layers of stacked syntheticfilter media. A “substantial portion of each layer of stacked syntheticfilter media” is intended to mean at least 50%, at least 60% or at least80% of the layers of synthetic filter media in the stack. The term“substantially unbonded” is used to mean that at least 97% of thesurface area of the layer of filter media is unbonded. In some suchembodiments, each layer of the stacked layers of synthetic filter media182 in the coalescing region 180 is substantially unbonded to adjacentlayers of synthetic filter media. In some other embodiments, however, atleast a portion of the layers of stacked synthetic filter media 182 arebonded to adjacent layers of synthetic filter media. In one exampleembodiment, a portion of the layers of stacked synthetic filter media182 are thermally bonded to adjacent layers of synthetic filter media.

Now the materials contemplated for coalescing filter media will bedescribed.

Coalescing Filter Media Description

Coalescing filter media consistent with the technology disclosed hereinis generally a wet laid media. The wet laid media can be constructedconsistently with, for example, U.S. Pub. No. 2012/0234748, filed onMar. 16, 2012 or, in another example, U.S. Pat. No. 7,314,497, issued onJan. 1, 2008, each of which are incorporated by reference herein. Thewet laid media is formed in a sheet by wet laid processing, formed intodisks, and is then inserted in the vent housing of the vent assembly.Typically, as described above, the wet laid media disks are stacked in aplurality of layers in the vent housing allowing gravity-assisteddrainage of coalesced oil.

The media composition of the wet laid sheets used to form the coalescingregion in a breather vent is typically as follows:

-   -   1. It is provided in a form having a calculated pore size (in        the X-Y direction, explained in more detail, below) of at least        10 micron, usually at least 12 micron. The pore size is        typically no greater than 80 micron, for example within the        range of 12-60 micron, typically 15-45 micron.    -   2. It is formulated to have a particle filtration efficiency (at        20 fpm for 0.78 micron particles), within the range of 3-18%,        typically 5-15%.    -   3. It is at least 30% by weight, typically at least 40% by        weight, often at least 45% by weight and in some embodiments        within the range of 85-95% by weight, based on total weight of        material within the sheet, bi-component fiber material in accord        with the general description provided herein.    -   4. It has 5 to 70%, by weight, based on total weight of material        within the sheet, a secondary fiber material disposed among the        bi-component fibers. This secondary fiber material can be a mix        of fibers. In a variety of embodiments, cellulose fibers are        used, but in some other embodiments glass microfibers are used.        Alternatives are possible. In one embodiment the coalescing        media has about 5-9%, or more particularly about 7.5%, cellulose        by weight, and the remaining 91-95% is bi-component fiber. In an        alternate embodiment the coalescing media has about 47-53%, or        more particularly about 50%, glass microfiber by weight and the        remaining 47-53% is bi-component fiber.    -   5. Typically the fiber sheet (and resulting filter media)        includes no added binder material (excluding the material        defining the fibers of the fiber sheet). If an added binder        material is present, generally it is present at no more than        about 7% by weight of the total fiber weight, and preferably no        more than 3% by weight of the total fiber weight.    -   6. Typically the wet laid media is made to a basis weight of at        least 20 lbs. per 3,000 square feet (9 kg/278.7 sq. m.), and        typically not more than 120 lbs. per 3,000 square feet (54.5        kg/278.7 sq. m.). Usually it will be selected within the range        of 35-130 lbs. per 3,000 sq. ft. (15.9 kg-54.4 kg/278.7 sq. m).        In one particular embodiment the media has a basis weight of        about 36.5 lbs to about 45.5 lbs. per 3,000 sq. ft.    -   7. Typically the wet laid media is made to a Frazier        permeability (feet per minute) of 15-500 feet per minute (12-153        meters/min.), typically 100 feet per minute (30 meters/min.).        For the basis weights on the order of about 35 lbs/3,000 square        feet-130 lbs./3,000 square feet (15.9-54.4 kg/278.7 sq. meters),        typical Frazier permeabilities would be about 300-600 ft./min.        (60-120 meters/min.), and in some other embodiments would range        from 15-50 ft/min.    -   8. The thickness of the wet laid media sheet(s) used to form the        described coalescing region in the vent assembly at 0.125 psi        (8.6 millibars) will typically be at least 0.01 inches (0.25 mm)        often on the order of about 0.018 inch to 0.07 inch (0.45-1.78        mm); typically 0.018-0.03 inch (0.45-0.76 mm). In one embodiment        the media sheet has a thickness of about 0.015 inch to about        0.023 inch at 1.5 psi.

A. Pore Size.

In general, if the pore size of the coalescing filter media is too low,drainage of coalesced oil particles by gravity, downwardly through (andfrom) the coalescing filter media can be difficult or slowed, whichleads to an increase of re-entrainment of the oil into the gas stream;and if the porosity is too high, oil particles are less likely tocollect and coalesce.

Barrier vents consistent with the technology disclosed herein canincorporate coalescing filter media having a pore size within the rangeof 12 to 80 micron. Typically the pore size is within the range of 15 to45 micron. At least a portion of the layers of coalescing filter mediathat are configured to first receive gas flow from the enclosure withentrained oil for designs characterized in the drawings, through a depthof at least 0.25 inch (6.4 mm), has an average pore size of at least 20microns. This is because in this region, a larger first percentage ofthe coalescing/drainage will occur. In upper layers, in which lesscoalescing drainage occur, a smaller pore size for more efficientfiltering of solid particles can be desirable in some instances. In avariety of embodiments, at least a portion of the coalescing filtermedia in the coalescing region of the vent assembly has an average poresize of about 30-50 microns.

The term pore size and variants thereof when used herein with referenceto the coalescing filter media, is meant to refer to the theoreticaldistance between fibers in a filtration media in the X-Y direction. X-Yrefers to the surface direction versus the Z direction, which is themedia thickness. The calculation assumes that all the fibers in themedia are lined parallel to the flow face of the media, equally spaced,and ordered as a square when viewed in cross-section perpendicular tothe length of the fibers. The pore size is a distance between the fibersurface on the opposite corners of the square. If the media is composedof fibers of various diameters, the d² mean of the fiber is used as thediameter. The d² mean is the square root of the average of the diameterssquared. The pore size of the media can be estimated by reviewingelectron photographs of the media. The average pore size of a media canalso be calculated using a Capillary Flow Porometer having Model No. APP1200 AEXSC available from Porous Materials, Inc. of Ithaca, N.Y.

Coalescing filter media in accord with the general definitions providedherein can have a mix of bi-component fibers and other fibers, and canbe used in a vent assembly as generally described herein in connectionwith the figures. Typically enough media sheets would be used in thecoalescing region to have an overall particle filtration efficiency ofat least 85%, typically 90% or greater. In some instances it would bepreferred to have the efficiency at 95% or more and even 99% or more.

B. Thickness

The thickness of media utilized to make the coalescing regions accordingto the present disclosure is typically measured using a dial comparatorsuch as an Ames #3 W (BCA Melrose Mass.) equipped with a round pressurefoot, one square inch. A total of 2 ounces (56.7 g) of weight is appliedacross the pressure foot.

Typical wet laid media sheets useable to be stacked to form coalescingregions according to the present disclosure have a thickness of at least0.01 inches (0.25 mm) at 0.125 psi (8.6 millibars), up to about 0.06inches (1.53 mm), again at 0.125 psi (8.6 millibars). Usually, thethickness will be 0.018-0.03 inch (0.44-0.76 mm) under similarconditions.

C. The Media Composition.

1. The Bi-Component Fiber Constituent.

As indicated above, it is preferred that the fiber composition of themedia include 30 to 95%, by weight, of bi-component fiber material. Amajor advantage of using bi-component fibers in the media, is effectiveutilization of fiber size while maintaining a relatively low solidity.With the bi-component fibers, this can be achieved while stillaccomplishing a sufficiently high strength media for handlinginstallation in vent assemblies.

The bi-component fibers generally comprise two polymeric componentsformed together, as the fiber. Various combinations of polymers for thebi-component fiber may be useful, but it is important that the firstpolymer component melt at a temperature lower than the meltingtemperature of the second polymer component and typically below 205° C.Further, the bi-component fibers are integrally mixed and evenlydispersed with the other fibers, in forming the wet laid media. Meltingof the first polymer component of the bi-component fiber is necessary toallow the bi-component fibers to form a tacky skeletal structure, whichupon cooling, captures and binds many of the other fibers, as well asother bi-component fibers.

Although alternatives are possible, typically the bi-component fiberswill be formed in a sheath core form, with a sheath comprising the lowermelting point polymer and the core forming the higher melting point.

In the sheath-core structure, the low melting point (e.g., about 80 to205° C.) thermoplastic is typically extruded around a fiber of thehigher melting point material (e.g., about 120 to 260° C.). In use, thebi-component fibers typically have a average largest cross-sectionaldimension (average fiber diameter, if round) of about 5 to 50 micrometeroften about 10 to 20 micrometer and typically in a fiber form generallyhave an average length of at least 1 mm, and not greater than 30 mm,usually no more than 20 mm, typically 1-10 mm. By “largest” in thiscontext, reference is meant to the thickest cross-section dimension ofthe fibers.

Such fibers can be made from a variety of thermoplastic materialsincluding polyolefins (such as polyethylenes, polypropylenes),polyesters (such as polyethylene terephthalate, polybutyleneterephthalate, PCT), nylons including nylon 6, nylon 6,6, nylon 6,12,etc. Any thermoplastic that can have an appropriate melting point can beused in the low melting component of the bi-component fiber while highermelting polymers can be used in the higher melting “core” portion of thefiber. The cross-sectional structure of such fibers can be a“side-by-side” or “sheath-core” structure or other structures thatprovide the same thermal bonding function. One could also use lobedfibers where the tips have lower melting point polymer. The value of thebi-component fiber is that the relatively low molecular weight resin canmelt under sheet, media, or filter forming conditions to act to bind thebi-component fiber, and other fibers present in the sheet, media, orfilter making material into a mechanically stable sheet, media, orfilter.

Typically, the polymers of the bi-component (core/shell or sheath andside-by-side) fibers are made up of different thermoplastic materials,such as for example, polyolefin/polyester (sheath/core) bi-componentfibers whereby the polyolefin, e.g. polyethylene sheath, melts at atemperature lower than the core, e.g. polyester. Typical thermoplasticpolymers include polyolefins, e.g. polyethylene, polypropylene,polybutylene, and copolymers thereof, polytetrafluoroethylene,polyesters, e.g. polyethylene terephthalate, polyvinyl acetate,polyvinyl chloride acetate, polyvinyl butyral, acrylic resins, e.g.polyacrylate, and polymethylacrylate, polymethylmethacrylate,polyamides, namely nylon, polyvinyl chloride, polyvinylidene chloride,polystyrene, polyvinyl alcohol, polyurethanes, cellulosic resins, namelycellulosic nitrate, cellulosic acetate, cellulosic acetate butyrate,ethyl cellulose, etc., copolymers of any of the above materials, e.g.ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers,styrene-butadiene block copolymers, Kraton rubbers and the like. Onetype of bi-component fiber that is contemplated is 271P available fromDuPont, based in Wilmington, Del. Other fibers include FIT 201, KurarayN720 and the Nichimen 4080 and similar materials. All of thesedemonstrate the characteristics of cross-linking the sheath polymer uponcompletion of first melt. This can be useful for oil applications wherethe application temperature is typically above the sheath melttemperature. If the sheath does not fully crystallize then the sheathpolymer will re-melt in application and coat or damage downstreamequipment and components.

An example of a useable bi-component fiber for forming wet laid mediasheets for use in the coalescing region of the breather vent is Dupontpolyester bi-component 271P, which can be cut to a length of about 6 mm.

2. The Secondary Fiber Materials.

The bi-component fibers provide a matrix for the coalescing filterregion. The secondary fibers sufficiently fill the matrix to provide thedesirable properties for efficiency, if increased efficiency isdesirable. In some embodiments secondary fibers are used to increase thestrength of the bi-component fiber matrix.

The secondary fibers can be polymeric fibers, glass fibers and/ormicrofibers, cellulose fibers, metal fibers, ceramic fibers or a mixtureof any of these. In at least one embodiment, cellulose fibers are theonly type of secondary fiber used with the bi-component fibers. In someother embodiments, glass fibers, polymeric fibers or a mixture are usedas the secondary fiber materials.

In some embodiments the coalescing filter media has glass microfibers.In some other embodiments the coalescing filter media substantiallylacks glass microfibers. Glass microfibers can be used in embodimentswhere relatively higher particle filtration efficiency is desirable anda relatively higher pressure drop is tolerable. Glass fibers useable infilter media of the present technology include glass types known by thedesignations: A, C, D, E, Zero Boron E, ECR, AR, R, S, S-2, N, and thelike, and generally, any glass that can be made into fibers either bydrawing processes used for making reinforcement fibers or spinningprocesses used for making thermal insulation fibers.

Non-woven media of the currently-described technology can containsecondary fibers made from a number of both hydrophilic, hydrophobic,oleophilic, and oleophobic fibers. These fibers cooperate with the glassfiber (if used) and the bi-component fiber to form a mechanicallystable, but relatively strong, permeable filtration media that canwithstand the mechanical stress of the passage of fluid materials andcan maintain the loading of particulate during use. Secondary fibers aretypically monocomponent fibers with average largest cross-sectionaldimension (diameters if round) that can range from about 0.1 micron andup, typically 1 micron or greater, often 15-55 microns, and occasionally8-15 microns, and can be made from a variety of materials includingnaturally occurring cotton, linen, wool, various cellulosic andproteinaceous natural fibers, synthetic fibers including rayon, acrylic,aramide, nylon, polyolefin, polyester fibers. One type of secondaryfiber is a binder fiber that cooperates with other components to bindthe materials into a sheet. Another type of secondary fiber is astructural fiber that cooperates with other components to increase thetensile and burst strength the materials in dry and wet conditions.Additionally, the binder fiber can include fibers made from suchpolymers as polyvinyl chloride, polyvinyl alcohol. Secondary fibers canalso include inorganic fibers such as carbon/graphite fiber, metalfiber, ceramic fiber and combinations thereof.

Thermoplastic fibers can be used as secondary fibers, as well, notlimited to polyester fibers, polyamide fibers, polypropylene fibers,copolyetherester fibers, polyethylene terephthalate fibers, polybutyleneterephthalate fibers, polyetherketoneketone (PEKK) fibers,polyetheretherlcetone (PEEK) fibers, liquid crystalline polymer (LCP)fibers, and mixtures thereof. Polyamide fibers include, but are notlimited to, nylon 6, 66, 11, 12, 612, and high temperature “nylons”(such as nylon 46) including cellulosic fibers, polyvinyl acetate,polyvinyl alcohol fibers (including various hydrolysis of polyvinylalcohol such as 88% hydrolyzed, 95% hydrolyzed, 98% hydrolyzed and 99.5%hydrolyzed polymers), cotton, viscose rayon, thermoplastic such aspolyester, polypropylene, polyethylene, etc., polyvinyl acetate,polylactic acid, and other common fiber types.

Mixtures of the fibers can be incorporated in the coalescing filtermedia, to obtain certain desired efficiencies and other parameters.

The coalescing filter media of the current disclosure are typically madeusing papermaking processes. Such wet laid processes are particularlyuseful and many of the fiber components are designed for aqueousdispersion processing. However, the media of the currently-describedtechnology can be made by air laid processes that use similar componentsadapted for air laid processing. The machines used in wet laid sheetmaking include hand laid sheet equipment, Fourdrinier papermakingmachines, cylindrical papermaking machines, inclined papermakingmachines, combination papermaking machines and other machines that cantake a properly mixed paper, form a layer or layers of the furnishcomponents, remove the fluid aqueous components to form a wet sheet. Afiber slurry containing the materials are typically mixed to form arelatively uniform fiber slurry. The fiber slurry is then subjected to awet laid papermaking process. Once the slurry is formed into a wet laidsheet, the wet laid sheet can then be dried, cured or otherwiseprocessed to form a dry permeable, but real sheet, media, or filter.

For a commercial scale process, the bi-component matrices of the currenttechnology are generally processed through the use of papermaking-typemachines such as commercially available Fourdrinier, wire cylinder,Stevens Former, Roto Former, Inver Former, Venti Former, and inclinedDelta Former machines. Preferably, an inclined Delta Former machine isutilized. A bi-component mat of the current disclosure can be preparedby forming a bi-component fiber slurry and a cellulose or glass fiberslurry and combining the slurries in mixing tanks, for example. Theamount of water used in the process may vary depending upon the size ofthe equipment used. The furnish may be passed into a conventional headbox where it is dewatered and deposited onto a moving wire screen whereit is dewatered by suction or vacuum to form a non-woven bi-componentweb.

The binder in the bi-component fibers is activated by passing the webthrough a heating step. The resulting material can then be collected ina large roll if desired.

3. Surface Treatments of the Fibers.

Modification of the surface characteristics of the fibers, such as toincrease the contact angle between the fiber and the oil, such as withan oleophobic treatment, can enhance drainage capability of thecoalescing region and prevent the sorption of oil by the fibers in thecoalescing region. A method of modifying the surface of the fibers is toapply a surface treatment such as a fluorochemical or siliconecontaining material, typically up to 5% by weight of the media. Suchtreatments can enhance the oleophobicity of the filter media.

The fibers of the coalescing filter media can generally be characterizedas oleophobic. Oleophobicity is typically imparted to the coalescingfilter media by depositing a layer of oleophobic fluorochemical on themedia fibers and/or by submerging the coalescing filter media in asolution of the fluorochemical (dip coating), among other means. Lickrolling, gravure coating, and/or curtain coating are some other exampleways that the coalescing filter media can be treated for oleophobicity.

The surface treatment agent can be applied during manufacture of thefibers, during manufacture of the media or after manufacture of themedia. Numerous treatment materials are available such asfluorochemicals or silicone containing chemicals that increase thecontact angle between the fibers and the particular type of oilof-interest. Particular surface treatments that are contemplated arediscussed in U.S. Pub. No. 2012/0234748, referenced above.

In more general terms, a coalescing region manages bothcoalescing/drainage of oil particulates and also filtration ofparticles. It can be desirable for the collected oil to drain rapidly;otherwise the functional life of the filter media would beuneconomically short. The media is positioned so the oil can drain fromthe media rapidly. Some key performance properties of the vent assemblyare: initial and equilibrium fractional efficiency, pressure drop anddrainage ability. Some key physical properties of the media are:thickness, solidity and strength.

Generally the media for coalescing/drainage is aligned in a manner thatenhances the filters ability to drain. In a variety of constructions,this would be a media configured in an elongate, vertical orientation.In this orientation, any given media composition will exhibit anequilibrium load height which is a function of the pore size, fiberorientation and the interaction of the oil with the fiber surface,measured as the contact angle. Collection of oil in the media willincrease in height to a point balanced with the drainage rate of the oilfrom the media. Of course any portion of the media that is plugged withdraining oil is not generally available for particle filtration. Thus,such plugged portions of the media cause an increase in pressure dropand a decrease in particle filtration efficiency of the filter. As aresult, it can be advantageous to control the portion of the coalescingregion that is most available to be plugged by oil. Alternately statedis it is advantageous to increase the drainage rate, particularly in aportion of the coalescing region closest to the enclosure.

The media properties effecting drainage rate are pore size, fiberorientation, and interaction of the oil being drained with the fibersurface. Such properties can be refined to accomplish a desirable oilflow. Increasing the pore size facilitates drainage, as explained above.However increasing the pore size reduces the number of fibers forfiltration, thus reducing the overall efficiency of the coalescingregion. To achieve target efficiency, a relatively thick coalescingregion can be formed by using multiple layers of material having adesirable pore size.

In a variety of embodiments a substantial portion of the layers ofcoalescing filter media is consistent with the disclosure of U.S. Pub.No. 2012/0234748, referenced above.

Returning to FIG. 2, the vent assembly 100 is configured to directcoalesced oil that has drained out of the coalescing region 180 into theenclosure 200. Gravity can aid in the draining of the coalesced oil outof the coalescing region 180. One or more run-off surfaces 118 definedby the vent housing 110 can direct the draining coalesced oil into theenclosure 200. The run-off surfaces 118 generally are positioned toreceive coalesced oil that is drained out of the coalescing region 180.The run-off surfaces 118 are ramped downwards towards the vent orifice204 of the enclosure 200 such that gravity can assist the draining ofthe coalesced oil into the enclosure 200. In the current embodiment thevent housing 110 defines a plurality of discrete run-off surfaces 118,but in some embodiments the vent housing 100 can define a single run-offsurface. In the current embodiment the plurality of discrete run-offsurfaces 118 are defined between substantially planar platform surfaces119 of the vent housing 110 on which the coalescing filter media 182 issituated.

FIG. 7 shows an example embodiment demonstrating an alternate run-offsurface 719 consistent with the technology disclosed herein. The ventassembly 700 is similar to those embodiments that have already been andwill be described herein, except in this embodiment the vent housing 710of the vent assembly 700 has a run-off surface 718 that defines a singlefluid draining pathway that is also a platform surface on which thecoalescing filter media 782 is stacked. As such, the coalescing filtermedia 782 is stacked at an angle that matches the angle of the run-offsurface 718. A mounting structure 720 defining an airflow pathway 750 ispositioned asymmetrically relative to the vent housing 710. The run-offsurface 718 is ramped downward towards the airflow pathway 750 such thatoil draining from the coalescing region 780 is directed toward theairflow pathway 750 to drain into an enclosure. A ledge region 719adjacent to the run-off surface 718 supports the stack of coalescingfilter media 782 along a circumferential portion of the base of thestack 782.

Returning again to FIG. 2, the spacing region 170 of the vent assembly100 is generally configured to prevent contact between oil from theenclosure 200 and the membrane 160. In particular, the spacing region170 can be configured to impede wicking of the oil towards the membrane160. The spacing region 170 can also be configured to prevent contactbetween the coalescing filter media 182 and the membrane 160. Thespacing region 170 can be a physical barrier between the coalescingregion 180 and the membrane 160. In at least one embodiment, the spacingregion 170 can be a physical barrier that is configured to contain thecoalescing filter media within the coalescing region.

In a variety of embodiments, including that depicted in FIG. 2, thespacing region 170 is at least partially defined by a media spacer 172.The media spacer 172 is disposed within the vent housing 110 between theelongate coalescing region 180, particularly the coalescing filter media182, and the membrane 160. The spacing region 170 is also defined by aphysical gap 174 between the media spacer 172 and the membrane 160. Inan alternate embodiment, the spacing region lacks a media spacer and ismerely a physical gap between the coalescing region and the membrane.

In the current embodiment, the media spacer 172 is generally configuredto prevent contact between the coalescing filter media 182 and themembrane 160. The media spacer 172 is also configured to define aportion of the airflow pathway 150 such that air flowing through thecoalescing region 180 towards the membrane 160 passes the media spacer172. In the currently described embodiment, the media spacer 172 extendsacross the airflow pathway 150 and defines a plurality of openings 174that define the airflow pathway 150. The plurality of openings 174 arevisible in FIG. 4, which depicts an exploded view of example ventassembly components without the vent housing 100.

The media spacer 172 can be constructed of a variety of types ofmaterials. For example, in some embodiments the media spacer 172 is amoldable material, such as plastic. In some embodiments the media spacer172 is machineable. In some embodiments, the media spacer 172 is afabric. Other configurations for a media spacer are possible. In onealternate example embodiment, a media spacer can have a ringconfiguration. In another example embodiment, a media spacer can be oneor more projections extending from the vent housing at least partiallyinto the airflow pathway. In yet another example embodiment, the mediaspacer can be a woven material that is configured to prevent wicking ofoil, such as by having a relatively thick fiber diameter.

The media spacer 172 is coupled to the vent housing 110. The mediaspacer 172 can be coupled to the vent housing 110 in a variety of ways,as will be appreciated. In a variety of embodiments, including thatdepicted in FIG. 2, the media spacer 172 and the vent housing 110 areconfigured to mutually engage. Particularly, the media spacer 172 andthe vent housing 110 mutually define an interference fit 116 thatsubstantially retains the position of the media spacer 172 relative tothe vent assembly 100. In such an embodiment the media spacer 172defines a coupling structure 116 a (See FIG. 4) that is configured to bereceived by a mating structure 116 b (see FIG. 3) of the vent housing110. In an alternative embodiment, the media spacer and the vent housingdefine threads that are configured to mutually engage. In someembodiments, the media spacer 172 can compress the stack of layers ofcoalescing filter media 182. In some other embodiments, the media spacerdoes not compress the stack of layers of coalescing filter media 182.

In an alternate embodiment consistent with FIG. 6, a vent assembly 500is similar to the vent assembly as has been and will be described hereinwith respect to FIG. 2, except that a media spacer 572 of the ventassembly 500 defines a perimeter region 576 in which the media spacer572 is coupled to the vent housing 510. The media spacer 572 can becoupled to the vent housing 510 with a weld, adhesive, or through othermeans generally known in the art. The media spacer is coupled to thevent housing 510 in a rim region 514 defined vent housing 510.

Returning back to FIG. 2, and as mentioned above, the vent housing 110generally defines an airflow pathway 150 that extends from the mountingstructure 120 to the external environment relative to the vent housing110 (such as the atmosphere). The airflow pathway 150 can becharacterized as being the combination of three airflow pathways thatare depicted in FIG. 2. A first airflow pathway 152 is configured forfluid communication with the interior of the enclosure 200. A secondairflow pathway 154 is configured for fluid communication with theexternal environment, and a third airflow pathway 156 extends betweenthe first airflow pathway 152 and the second airflow pathway 154. Thesecond airflow pathway 154 extends from the membrane 160 to the externalenvironment through the perimeter openings 140 defined by the venthousing 110. The membrane 160 is coupled to the vent housing 110 suchthat the second airflow pathway 154 and the third airflow pathway 156are in communication through at least a portion of the membrane 160. Thestack of layers of coalescing filter media 182 is disposed within thevent housing 110 such that the third airflow pathway 156 and the firstairflow pathway 152 are in communication through at least a portion ofthe coalescing filter media 182. The media spacer 172 can be configuredto define a portion of the third airflow pathway 156.

The vent cap 130 is coupled to the vent housing 110 and is generallyconfigured to shield a flow face 162 (See FIG. 4) of the membrane 160from the environment. The perimeter openings 140 defined by the venthousing 110 are generally defined to similarly shield the flow face 162of the membrane 160 from the environment. Shielding the flow face of themembrane is intended to mean that the relevant features of the ventassembly are configured to prevent environmental contaminants fromdirectly impacting the flow face of the membrane.

Vent Assembly Testing

A test was designed and constructed to compare and evaluate theperformance of breather vents with efforts made to simulate real-worldconditions that may be encountered by such a vent. An Example BreatherVent was consistent with the embodiment depicted in FIGS. 1-5 and had amicroporous PTFE membrane laminated to a non-woven nylon support layercoupled to a vent housing, an oleophobic coalescing region havingbi-component polyester fibers and about 7.5% by weight cellulose fibers,and a spacing region between the microporous membrane and the coalescingregion. A Comparative Breather Vent was also tested which was the VE2048breather vent provided by Gore Enterprises based in Newark, Del. TheComparative Breather Vent had a microporous membrane coupled to a venthousing and sorbent fibers disposed in the housing between a mountingregion and the microporous membrane.

A schematic depiction of the test set up is shown in FIG. 8. A steadyflow of heated oil aerosol was directed through the heated enclosure 300and up through the sample vents 312-318 to be tested, while the pressuredrop across the vents 312-318 was recorded. Particular details regardingthe test set-up will now be described.

Compressed air, pressurized at 1 bar, was supplied to a Palas PLG-2110Aerosol Generator 320 filled with Mopar SAE 75 W-140 Synthetic lubricantmaintained at a temperature of 90° C. The flow of oil particles producedby the aerosol generator 320, at a rate of 0.43 grams of oil per hour,was directed into a cylindrical chamber 330 into which four steel tubes332 were inserted. The opening of each tube 332 was positioned facingthe flow, such that some oil aerosol was directed into each tube 332,and the remaining flow was allowed to pass through the cylinder 330 assystem exhaust 380. Each steel tube 332 was connected to the inlet of avent 310 to be tested. The cylindrical chamber 330, vents 310, andtubing were all placed within a heated enclosure 300 with a maintainedtemperature of 90° C. Cole Parmer flowmeters 340 with a range of 20-200mL/min were connected downstream of the breather vents 310 to measurethe rate of flow through each vent 310. Each flowmeter 340 was thenconnected to a needle valve 350, which was connected to a vacuum pump360.

Taps were added upstream and downstream of each vent 310 and connectedto a Setra pressure transducer 370 to measure the pressure differentialacross each vent 310. Two transducers had a range of 0-50 inches H₂O,and two had a range of 0-100 inches H₂O, and all four were powered by asingle 24V/4.17A DC power supply. Data was collected by a NationalInstruments USB-6001 data acquisition system, and recorded in NationalInstruments LabVIEW software. The pressure transducers 370 werecalibrated by comparing voltage measurements from the transducer to thepressure differential measured by a calibrated Meriam M100 digitalmanometer.

FIG. 9 is a graph depicting comparative test results of the ventassemblies discussed above, demonstrating the amount of time needed foreach vent to reach a differential pressure of 0.18 psi. As isdemonstrated, the Example Breather Vent had a lower differentialpressure over time. An increase in the differential pressure is anindicator of obstruction of the pores in the filter media by the oilparticles in the aerosol as the oil particles accumulate. The data inFIG. 9 suggests that the Example Breather Vent has a longer useful lifethan the Comparative Breather Vent. Much of the performance improvementin pressure drop of the Example Breather Vent is thought to beattributable to the use of (1) an oleophobic coalescing filter media and(2) media having an open pore structure of the Example Breather Vent,instead of the oil-sorbent filter media used in the Comparative BreatherVent. Since the coalescing region of the Example Breather Vent does notabsorb/adsorb the oil, the oil is more likely to drain and, therefore,less likely to obstruct the pores in the filter media. Test datadepicted in FIGS. 10-13, described below, further supports thisconclusion.

With regard to test data reflected in FIG. 10, the lower 0.08 inches ofa 0.5-inch vertical stack of a coalescing filter media (consistent witha coalescing region 180, discussed above with reference to FIGS. 1-5)and an equally-sized vertical stack of an oil-sorbent filter media weresubmerged in a container of liquid oil for over seven hours. The oil wasMopar SAE 75 W-140 Synthetic lubricant. The oil-sorbent filter media wasnot oleophobic and had untreated cellulose fibers with a layer ofuntreated polypropylene fibers disposed within the stack. The coalescingregion had coalescing filter media having bi-component polyester fibersand about 7.5% cellulose fibers by weight. The coalescing filter mediawas treated to be oleophobic. The mass of each stack of filter media wasrecorded incrementally to track the total mass of oil that wasabsorbed/adsorbed by each filter.

As demonstrated in FIG. 10, the sorbent media accumulated over 2 gramsof oil, while no appreciable amount of oil accumulated in the coalescingfilter media. Visual inspection of the media stacks revealed that theoil wicked vertically up the entire length of the stack of sorbentfilter media extending above the liquid oil (0.42-inches), whereas theoil did not wick vertically up the stack of coalescing filter mediaextending above the liquid oil. The data of FIG. 10 supports theconclusion from FIG. 9 that some coalescing regions consistent with thetechnology disclosed herein are not sorbents of liquid oil because theydo not accumulate an appreciable amount of oil in a wick test, where theliquid oil is consistent with the type of oil used in the environment inwhich the filter media will be used. Similarly, some coalescing regionsconsistent with the technology disclosed herein are not sorbents ofliquid oil because they do not wick liquid oil up vertically through thecoalescing region, against gravity. It is expected that an increasedability of a media to absorb/adsorb liquid oil can reduce barrier ventlife because the entrained oil that is captured by the media eventuallyaccumulates into a pooled mass of oil that is retained by the media andobstructs pores. It is noted that the term “liquid oil,” for purposes ofthis disclosure, refers to a pooled mass of oil that is not entrained ina gas.

FIG. 11 depicts test data collected that is associated with similar testset-up as that described with reference to FIG. 8, except that in thistest a relatively high airflow was used of 14 liter/min to observe thepressure drop across the coalescing region of a barrier vent as it isloaded with oil. Because of the high airflow used, theaerosol-impregnated airstream was directed downwardly through thecoalescing region so as not to counteract the effect of gravity ondraining the coalesced oil from the coalescing region. For that reason,and to observe the characteristics of the coalescing region alone, amembrane, a cap, and a spacer were omitted from the tested ventassembly. The results depicted in FIG. 11 demonstrate that the pressuredifferential across the coalescing filter media appears to substantiallyplateau as time passes. This result appears to be consistent with theconclusion that after a threshold mass of entrained oil is loaded in thecoalescing filter region, the coalescing filter region reaches asubstantially steady-state where the mass of oil draining from thecoalescing filter region is doing so at a similar rate as the mass ofoil being introduced into the coalescing filter region.

In a variety of embodiments consistent with the technology disclosedherein, a substantial portion of the layers of filter media within thecoalescing region will not absorb or adsorb a droplet of liquid oil,where a “substantial portion” refers to at least 95%, 99% or 100% of thelayers of filter media, and the liquid oil is consistent with the typeof oil used in the environment in which the filter media will be used. Atest was conducted comparing a coalescing sheet of filter media from thecoalescing region of the technology disclosed herein to an oil-sorbentsheet of filter media from the VE2048 breather vent by Gore Enterprises.The coalescing sheet of filter media had 7.5% cellulose fibers by weightand the remaining content was bi-component polyester fibers. Thecoalescing sheet of filter media had an oleophobic treatment. Theoil-sorbent sheet of filter media was cellulose fibers that were nottreated to be oleophobic. A droplet of liquid gear oil (Mopar SAE 75W-140) was placed on a surface of each of the types of filter media.FIGS. 12a and 12b is a schematic drawing representing the coalescingsheet of filter media and the oil-sorbent sheet of filter media,respectively, after dropping the oil onto their surfaces. As isdemonstrated, the droplet on the coalescing sheet of filter mediaremains substantially intact on the surface of the sheet of filtermedia, while the droplet on the oil-sorbent sheet of filter media iscompletely absorbed by the sheet of filter media.

In a variety of embodiments consistent with the technology disclosedherein, a substantial portion of the fibers in the filter media withinthe coalescing region are oleophobic and are not a sorbent of oil, where“a substantial portion” refers to at least 95%, 99%, and can be 100% ofthe fibers in the coalescing region, and the oil is consistent with thetype of oil used in the environment in which the filter media will beused. A test was conducted comparing the fibers in the coalescing sheetof filter media to the fibers in the oil-sorbent sheet of filter mediafrom the VE2048 breather vent, each described above with regard to FIGS.12a-12b . Photos were taken to document the interaction between dropletsof liquid gear oil (Mopar SAE 75 W-140) and each of the types of fibers,and contact angles between the fibers and the oil droplet were recordedand averaged. The contact angle is a measurement of the line defined bythe outer contact points (L, R, See FIGS. 13a-13c ) between the dropletand the fiber and the lines tangent to the droplet where it intersectsthe fiber.

FIG. 13a is a schematic drawing depicting the contact angle between anexample oil droplet and a bi-component fiber of the coalescing filtermedia. The contact angle had an average of about 124.5°±2.6°, comparingmultiple samples. FIG. 13b is a schematic drawing depicting the contactangle between an example oil droplet and the cellulose fiber of thecoalescing filter media. The samples tested had a contact angle averageof about 98.5°±2.8°. FIG. 13c is a schematic drawing depicting thecontact angle between an example oil droplet and a cellulose fiber fromthe oil-sorbent media. The measured contact angles had an average ofabout 87.4°±1.5°. Generally oil-sorbent fibers will have a contact angleof less than 90° with the oil droplet, indicating that at least some ofthe oil from the droplet is forming a film along the surface of thefiber. Oleophobic coalescing fibers, on the other hand, will have acontact angle of greater than 90° with the oil droplet.

Method

FIG. 14 is a flow chart depicting one method consistent with thetechnology disclosed herein. The method 400 is generally consistent withmaking a vent assembly.

A vent housing is formed 410. Layers of coalescing filter media arestacked in the housing 420. A media spacer is inserted in the housing430. A membrane is coupled to the housing 440. A cap is coupled to thehousing 450.

The vent housing is generally formed 410 to have a first end and asecond end, and to define an airflow pathway extending from the firstend to the second end. The vent housing can be formed 410 consistentlywith approaches that will generally be understood in the art. In oneembodiment, the vent housing is formed 410 through an injection moldingprocess. In another embodiment, the vent housing is formed 410 throughblow molding. The vent housing can be formed 410 from a variety ofmaterials and combinations of materials. In one embodiment the venthousing is formed 410 from one or more of nylon, polyamide, glass-filledpolyamide, polybutylene terephthalate, glass-filled polybutyleneterephthalate, high-density polyethylene, and/or polypropylene.

When stacking a plurality of layers of coalescing filter media in thehousing 420, the plurality of layers of coalescing filter media aregenerally stacked within the airflow pathway. Stacking the plurality oflayers in the airflow pathway of the housing can be executed such thatsome of the layers of the coalescing filter media are non-aligned withsome other of the layers of coalescing filter media. Non-alignment of atleast a portion of the plurality of layers of coalescing filter mediacan have the advantage of preventing air within the breather vent frombypassing the coalescing filter media.

Similar to the embodiments described above, a majority of the pluralityof layers of the coalescing filter media each has a maximum particlefiltration efficiency of 10%, such as an efficiency of 7%. In someembodiments at least 50 layers of coalescing filter media are stackedwithin the vent housing. In one particular embodiment, about 90 layersof coalescing filter media are stacked within the vent housing. In someembodiments, each layer of stacked coalescing filter media issubstantially unbonded to adjacent layers of stacked coalescing filtermedia. The coalescing filter media can be a variety of materials andcombinations of materials, as described above.

In some embodiments a secondary layer of coalescing filter media can bestacked in the vent housing, wherein the secondary layer of coalescingfilter media has a particle filtration efficiency of at least 48%. Inone particular embodiment the secondary layer of coalescing filter mediahas an efficiency of at least 60%. The secondary layer of coalescingfilter media can be positioned towards the top portion of the stack ofthe plurality of layers of coalescing filter media. In one embodimentthe secondary layer of coalescing filter media can be positioned betweenthe remaining layers of coalescing filter media and the membrane. Thecoalescing region can have an overall particle filtration efficiency ofat least 95%, and a pressure drop of less than 1.2 psi at 1.2 meters persecond, as has been described herein.

Inserting a media spacer in the housing 430 can aid in containing theplurality of layers of coalescing filter media in the housing. In onepreferred embodiment, the media spacer and the vent housing mutuallydefine an interference fit such that inserting the media spacer in thehousing 430 causes a coupling structure defined by the media spacer toengage a mating structure defined by the vent housing. In an alternateembodiment, the media spacer may be bonded to the vent housing, such asby a thermal weld.

The membrane is generally coupled to the vent housing 440 in a spacedrelationship from the coalescing filter media. In a variety ofembodiments the membrane is coupled to a membrane receiving surface 440defined by the vent housing. In one embodiment, the membrane is coupledto the vent housing 440 with an adhesive. In another embodiment, themembrane is coupled to the vent housing 440 by a weld, such as a thermalweld or ultrasonic weld.

In a variety of embodiments, the method of making a vent assembly canhave the additional step of coupling a cap to the housing 450 to shielda flow face of the membrane from the environment. The cap can bepositioned substantially parallel to the flow face of the membrane, insome embodiments.

It should also be noted that, as used in this specification and theappended claims, the phrase “configured” describes a system, apparatus,or other structure that is constructed or configured to perform aparticular task or adopt a particular configuration. The phrase“configured” can be used interchangeably with other similar phrases suchas “arranged”, “arranged and configured”, “constructed and arranged”,“constructed”, “manufactured and arranged”, and the like.

All publications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thistechnology pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated by reference.

This application is intended to cover adaptations or variations of thepresent subject matter. It is to be understood that the abovedescription is intended to be illustrative, and not restrictive.

We claim:
 1. A vent assembly comprising: a vent housing comprising amounting structure; a membrane coupled to the vent housing; a coalescingregion between the mounting structure and the membrane; a spacing regionbetween the coalescing region and the membrane; an airflow pathwayextending through the mounting structure, wherein the airflow pathwayfurther extends from the mounting structure to the environment externalto the vent housing through the coalescing region, the spacing region,and the membrane; and a draining pathway from the coalescing regionthrough the mounting structure along the airflow pathway.
 2. The ventassembly of claim 1, wherein the coalescing region comprises coalescingfilter media.
 3. The vent assembly of claim 2, wherein the coalescingfilter media comprises a plurality of layers of synthetic filter media.4. The vent assembly of claim 3, wherein each of the layers of syntheticfilter media has a central axis, and a plurality of the central axes arenot collinear.
 5. The vent assembly of claim 3, wherein each layer ofsynthetic filter media is substantially unbonded to adjacent layers ofsynthetic filter media.
 6. The vent assembly of claim 3, wherein thecoalescing region further comprises a secondary layer of synthetic,coalescing filter media, wherein the secondary layer of coalescingfilter media has a particle filtration efficiency of at least 48%. 7.The vent assembly of claim 1, wherein the coalescing region comprisesbi-component fibers.
 8. The vent assembly of claim 1, wherein thecoalescing region comprises polyester.
 9. The vent assembly of claim 1,wherein the coalescing region lacks a binder material.
 10. The ventassembly of claim 1, wherein the coalescing region is oleophobic. 11.The vent assembly of claim 1, wherein the coalescing region comprisesglass fibers.
 12. The vent assembly of claim 11, wherein the glassfibers are microfibers.
 13. The vent assembly of claim 1, wherein thecoalescing region has an overall particle filtration efficiency of atleast 95%.
 14. The vent assembly of claim 1, further comprising a mediaspacer between the coalescing region and the membrane, wherein the mediaspacer is configured to prevent contact between the coalescing regionand the membrane, and the airflow pathway extends through the mediaspacer.
 15. The vent assembly of claim 14, further comprising aninterference fit between the media spacer and the vent housing.
 16. Thevent assembly of claim 1, wherein the housing defines perimeter openingssuch that the airflow pathway extends from the membrane to the externalenvironment through the perimeter openings.
 17. The vent assembly ofclaim 1, further comprising a cap coupled to the housing, wherein thecap is configured to shield a flow face of the membrane from theenvironment.
 18. A method of making a vent assembly, comprising: forminga vent housing having a first end and a second end, wherein the venthousing comprises a mounting structure, and the vent housing defines anairflow pathway through the mounting structure; inserting coalescingfilter media in the airflow pathway within the housing to define acoalescing region of the vent assembly within the airflow pathway;inserting a media spacer to contain the coalescing filter media in thehousing; and coupling a membrane to the vent housing in a spacedrelationship from the coalescing filter media, wherein the membrane isdisposed across the airflow pathway, the coalescing region is betweenthe mounting structure and the membrane, a spacing region is definedbetween the coalescing region and the membrane, the airflow pathwayextends from the mounting structure to the environment external to thevent housing through the coalescing region, the spacing region, and themembrane, and a draining pathway is defined from the coalescing regionthrough the mounting structure along the airflow pathway.
 19. The methodof claim 18, further comprising coupling a cap to the housing to shielda flow face of the membrane from the environment.
 20. The method ofclaim 18, wherein the coalescing filter media is oleophobic.